Method and apparatus for rotating an image

摘要

In a method and an an apparatus for rotating a source image about a reference point on a reference coordinate axis through an arbitrary angle theta to obtain a destination image, the source image is represented by a group of reference blocks. Each of the reference blocks has NxN pixels and is composed of a square having a side parallel to an axis which is rotated relative to the reference coordinate axis by an angle of x theta . One of vertexes of each of the reference blocks is defined as a rotation center vertex. Each of the reference blocks is rotated about the rotation center vertex by an angle of theta to obtain a rotation block. Calculations are made on shift quantities DELTA Y and DELTA X of the rotation center vertex of each of the rotation blocks. The shift quantities DELTA Y and DELTA X result from a rotation of the rotation center vertex about the reference point through an angle of theta . The shift quantity DELTA Y is defined as extending along the reference coordinate axis, and the shift quantity DELTA X is defined as extending perpendicular to the reference coordinate axis. The rotation block is translated in a direction of the reference coordinate axis by the shift quantity DELTA Y, and is translated in a direction perpendicular to the reference coordinate axis by the shift quantity DELTA X to obtain the destination image.